As technology advances, the quality control of particular web (sheet and roll) products become increasingly important. These web products may be required to be completely free of certain kinds of flaws (“catastrophic” flaws), or to not exceed a certain number of flaws per unit area. Even though these may be specified in the product specifications, and in the purchaser's contract, there are no simple ways to certify or verify the actual quality of the web product.
One example of a type of catastrophic flaws are lithium-ion battery membrane flaws which can cause a watch battery to fail explosively. Other examples of catastrophic flaws in web products include bio-tech filter failure which allow bacteria into medications that could be fatal to a patient with a suppressed immune system, or a radiologist with one look at an x-ray film with a coating defect will never use that brand of film again.
Consequently, in recent years, considerable effort has been directed toward visual web inspection to enhance the uniform quality of material webs, such as these battery membranes and filter materials, as well as paper, glass, plastic, textiles, metallic sheets, fiberglass and sheet substrates. These web inspection systems are capable of high speed, high-resolution detection and classification of surface imperfections in continuously manufactured products at rates in excess of 500 inches per second. Such surface imperfections include tears, through-holes, abrasions and scattering imperfections, impurities preventing local processing, stains and absorbing imperfections, pinch marks, thickness imperfections, and other far side and near side imperfections.
Briefly, web inspection assemblies often include; an illumination source generating a point of light or a strip of light, and a photoelectric light sensor device or a conventional linear Charge Coupled Device (CCD) array or camera strategically positioned and angled to receive diffusely reflected light from a target surface illuminated by the generated light. Due to the scattering imperfections on or in the target surface, differences in light intensity of the reflected or transmitted light will be detected which may represent one of the above-mentioned surface imperfections. The light sensor device then delivers a signal to an electronic processing device representative of the type and magnitude of the surface imperfection.
These current web inspection systems, however, are limited in several respects. For instance, the current automated web inspection systems require hundreds of variables (inspection parameters) that need to be precisely set to enable a proper inspection. However, these settings may be unintentionally (or intentionally!) modified, which skews flaw detection and reporting. Moreover, these systems use proprietary software file structures that thwart verification of setup parameters, calibration, and open diagnostic monitoring of the inspection system.
Other problems associated with these current inspection systems is that they use proprietary Graphic User Interfaces (GUIs) that require anyone accessing the system to be physically present at the system's computer on the factory floor. Further, these proprietary inspection system file structures do not have the open architecture that enables easy tracking and verification of the hundreds of parameters necessary to verify and certify flaw detection reporting adequately to certify production to purchase orders corresponding to a specific web roll or web products.
Moreover, the current web inspection assemblies do not allow for secondary inspection or the web. When electronic Roll Maps of the web roll are recorded during prior inspections of the web material, the web surfaces are often not properly synchronized to effectively and precisely outline the flaw types and their locations. The specific location of the flaw, and the flaw type, cannot be accurately determined and classified along the web roll. This is particularly detrimental when the web products require a series of downstream applications at the same or different manufacturing systems. In this situation, even if the type of flaws and their locations are determined, the accuracy of such information deteriorates quickly.
As a result, the presence of a few detected flaws, affecting only a tiny fraction of the total material, will cause an entire lot (i. e., web roll) to be rejected. This is primarily due to the fact that although the flaws have been detected, their exact locations along the web are not accurately known, if they are known at all. Thus, separation or removal of the defective material from the remaining web portions cannot be precisely performed. Consequently, vast quantities of these good quality materials are unnecessarily discarded.
The quality control sought, therefore, is difficult to quantify, verify, and guarantee, even with expensive and labor-intensive initiatives to synchronize inspection results to existing process databases. These defect-critical products are manufactured and sold with little more than promises and good intentions of quality, certification of fitness for use, and compliance with purchase orders.
Accordingly, an apparatus and method of web inspection is needed which enables certification and verification of the actual quality of the web product.